iphone 5 doesn´t work after an ios 8.2 update via itunes

I was updating my iphone 5 model A1429 via itunes on my windows 7 computer, it was extracting the software when my computer died and it showed the apple icon and a grey progress bar on the iphone. When I turned on my computer again the itunes said "unexpected error occured, couldn´t update the phone" or something like that and that´s it. Since then itunes doesn´t recognize my device and on my iphone there is still the apple icon and the grey progress bar.
What can I do?